Citrus fruit is considered among the highest value fruit crop found in both tropical and sub-tropical countries of the world, Uganda inclusive.
The fruit plays a key role in human diets as a high source of vitamin C and other important nutrients, including folate a water-soluble vitamin, potassium and fibre. In a 2018 publication in Journal of Entomology and Zoology Studies by a team of agriculture scientists about distribution, abundance and severity of citrus pests in northern Uganda, it is stated that Brazil, United States and China continue to be the three largest processed orange producing regions in the world, taking up 85 per cent of the market.
It is stated that in East Africa, citrus is an important crop and production is estimated at 10 tonnes per hectare below the demand and the expected yield of 50 to 70 tonnes per hectare.
However, the decline in production by these countries is attributed to pests and diseases, despite the immense potential to export to the European Union.
In Uganda, the sweet orange citrus sinensis whose leaves and leaf buds are used to produce tea is the most widely grown and produced for both domestic consumption and regional markets. Majority of citrus trees are grown in either plantations or with a few fruit trees around homesteads.
Production is characterised by low inputs in terms of pest and disease control, use of improved planting materials and soil fertility enrichment measure. As such there is a concerted effort by stakeholders in a bid to help farmers address the challenge of pests and diseases.
Scientists at National Agricultural Research Organisation (Naro) are carrying out management of citrus fruit farming and evaluating pest and diseases affecting the fruit in eastern Uganda. The project is in its third phase under the Korea Programme on International Agriculture (Kopia) Uganda.
Dr John Adriko, who is handling the project on citrus covering districts of Bukedea, Kaberamaido, Kumi, Ngora and Soroti among others, explains that farmers have been sensitized about disease management.
The most common disease experienced by farmers growing citrus fruit in eastern Uganda is the pseudocercospora fruit and leaf spot, which destroys the fruit and leaves.
There is also altrenario brown spot, which usually causes a dark spot on the fruit, and anthracnose, which causes hard black spots on the fruit. The pests include aphids which attack the tree by sucking the sap out of the leaves, scales insects which cause leaves to yellow, leaf miners where the larvae feed by creating shallow tunnels in young leaves, as well as orange dogs which affects the fruit. The fruit flies, accompanied with diseases, will cause 100 per cent losses.
The pest and disease challenge may arise due to climatic conditions, including water stress in the fields and poor management practices.
Case study to establish measures for farmers to adopt
Dr Adriko and his team set up disease management experiments in Kaberamaido, Bukedea and Kumi and soil water management experiments set up in Soroti and Ngora. They carried out fruit quality assessment and trainings were conducted in citrus disease and soil water management. In a study conducted on farmer fields in Kaberamaido, Kumi and Bukedea in management of leaf spot disease indicated there was reduction in the disease rate as per the chemical applied.
Farmers who applied carbendazim chemical as an alternative to ridomil saw the disease rate reducing to 40.6 per cent. Those using copper combined with ridomil achieved 36.6 per cent, those who applied carbendazim alone achieved 30.6 per cent reduction and those who used copper fungicide attained 32.5 per cent reduction.
With the trainings conducted, farmers are slowly adopting the technologies and there is increased knowledge in disease management using the right chemical.
This is seen with 50 per cent decrease in pseudocercospora incidence in project fields in Bukedea, Kumi and Kaberamaido districts.
Farmers have also been trained on nursery management and in the entire crop management they have been sensitised on pesticide use, timely pruning, identification of soil fertility and spacing. Other measures include thinning, scouting, correct planting period, proper sanitation, fertiliser use and cover cropping.
Farmers are expected to carry out mulching, dig ridges, shallow trenches/channels to absorb water in the fields during dry seasons. They must also practice roadside water harvesting, use water basins for trapping rain water in the soil and also the application of manure at the appropriate time.
Farmers who are adopting these management practices are realising better performing citrus crops with more green leaves, bigger fruit observed in their farms.
All the fruit sampled depending on the variety performed above the normal fruit. The acidity level in the juice was generally low rated and one percent and the pH within the optimum range of 3 - 4.5.
A total of 93 farmers have so far been trained in disease management and 337 in soil water management. This is through practical illustrations on demonstration fields, provision of disease calendars, including disease management manuals.
They established that farmers focus on one approach at a time resulting in disease managed field seriously affected by drought and vice versa, there is need for using integrated approach. Farmers have challenges accessing inputs and this calls for intervention of cooperative unions. There is the challenge of poor market and marketing arrangements leading to farmers in districts of Kaberamaido, Kumi and Bukedea sometimes selling a bag of 100 kilogramme of the fruit at Shs30,000 while those in Soroti District will sell at Shs80,000.